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Regular Expression

정규표현

定規表現 규칙이 정해진 표현

아래 내용은 위키피디아 내용을 단순 짜집기하였다.(https://ko.wikipedia.org/wiki/정규_표현식)

Syntax[편집 | 원본 편집]

Delemiters[편집 | 원본 편집]

'/'를 사용하는 경우가 있다.

Standards[편집 | 원본 편집]

POSIX basic and extended[편집 | 원본 편집]

Metacharacter 기능 Description
^ 처음 Matches the starting position within the string. In line-based tools, it matches the starting position of any line.
. 문자 Matches any single character (many applications exclude newlines, and exactly which characters are considered newlines is flavor-, character-encoding-, and platform-specific, but it is safe to assume that the line feed character is included). Within POSIX bracket expressions, the dot character matches a literal dot. For example, a.c matches "abc", etc., but [a.c] matches only "a", ".", or "c".
[ ] 문자 클래스 A bracket expression. Matches a single character that is contained within the brackets. For example, [abc] matches "a", "b", or "c". [a-z] specifies a range which matches any lowercase letter from "a" to "z". These forms can be mixed: [abcx-z] matches "a", "b", "c", "x", "y", or "z", as does [a-cx-z].

The - character is treated as a literal character if it is the last or the first (after the ^, if present) character within the brackets: [abc-], [-abc]. Note that backslash escapes are not allowed. The ] character can be included in a bracket expression if it is the first (after the ^) character: []abc].

[^ ] 부정 Matches a single character that is not contained within the brackets. For example, [^abc] matches any character other than "a", "b", or "c". [^a-z] matches any single character that is not a lowercase letter from "a" to "z". Likewise, literal characters and ranges can be mixed.
$ 끝 Matches the ending position of the string or the position just before a string-ending newline. In line-based tools, it matches the ending position of any line.
( ) 하위식 Defines a marked subexpression. The string matched within the parentheses can be recalled later (see the next entry, \n). A marked subexpression is also called a block or capturing group. BRE mode requires \( \).
\n 일치하는 n번째 패턴 Matches what the nth marked subexpression matched, where n is a digit from 1 to 9. This construct is vaguely defined in the POSIX.2 standard. Some tools allow referencing more than nine capturing groups. Also known as a backreference.
* 0회 이상 Matches the preceding element zero or more times. For example, ab*c matches "ac", "abc", "abbbc", etc. [xyz]* matches "", "x", "y", "z", "zx", "zyx", "xyzzy", and so on. (ab)* matches "", "ab", "abab", "ababab", and so on.
{m,n} m회 이상 n회 이하 Matches the preceding element at least m and not more than n times. For example, a{3,5} matches only "aaa", "aaaa", and "aaaaa". This is not found in a few older instances of regexes. BRE mode requires \{m,n\}.

POSIX extended[편집 | 원본 편집]

Metacharacter 기능 Description
? 0 또는 1회 Matches the preceding element zero or one time. For example, ab?c matches only "ac" or "abc".
+ 1회 이상 Matches the preceding element one or more times. For example, ab+c matches "abc", "abbc", "abbbc", and so on, but not "ac".
| 선택 The choice (also known as alternation or set union) operator matches either the expression before or the expression after the operator. For example, abc|def matches "abc" or "def".

Character classes[편집 | 원본 편집]

POSIX Non-standard Perl/Tcl Vim Java ASCII Description
[:ascii:] \p{ASCII} [\x00-\x7F] ASCII characters
[:alnum:] \p{Alnum} [A-Za-z0-9] Alphanumeric characters
[:word:] \w \w \w [A-Za-z0-9_] Alphanumeric characters plus "_"
\W \W \W [^A-Za-z0-9_] Non-word characters
[:alpha:] \a \p{Alpha} [A-Za-z] Alphabetic characters
[:blank:] \s \p{Blank} [ \t] Space and tab
\b \< \> \b (?<=\W)(?=\w)|(?<=\w)(?=\W) Word boundaries
\B (?<=\W)(?=\W)|(?<=\w)(?=\w) Non-word boundaries
[:cntrl:] \p{Cntrl} [\x00-\x1F\x7F] Control characters
[:digit:] \d \d \p{Digit} or \d [0-9] Digits
\D \D \D [^0-9] Non-digits
[:graph:] \p{Graph} [\x21-\x7E] Visible characters
[:lower:] \l \p{Lower} [a-z] Lowercase letters
[:print:] \p \p{Print} [\x20-\x7E] Visible characters and the space character
[:punct:] \p{Punct} [][!"#$%&'()*+,./:;<=>?@\^_`{|}~-] Punctuation characters
[:space:] \s \_s \p{Space} or \s [ \t\r\n\v\f] Whitespace characters
\S \S \S [^ \t\r\n\v\f] Non-whitespace characters
[:upper:] \u \p{Upper} [A-Z] Uppercase letters
[:xdigit:] \x \p{XDigit} [A-Fa-f0-9] Hexadecimal digits

Examples[편집 | 원본 편집]

  메타문자 ;; 메타문자들의 열은 표현할 정규식을 지정한다.
   =~ m//  ;; 펄에서 문자열을 '일치'시키려는 동작을 지정한다.
   =~ s/// ;; 펄에서 문자열을 '대체'시키려는 동작을 지정한다.
Meta­character(s) Description Example
. Normally matches any character except a newline.

Within square brackets the dot is literal. 

$string1 = "Hello World\n";
if ($string1 =~ m/...../) {
  print "$string1 has length >= 5.\n";
}

Output: 

Hello World
 has length >= 5.
( ) Groups a series of pattern elements to a single element.

When you match a pattern within parentheses, you can use any of $1, $2, ... later to refer to the previously matched pattern. 

$string1 = "Hello World\n";
if ($string1 =~ m/(H..).(o..)/) {
  print "We matched '$1' and '$2'.\n";
}

Output: 

We matched 'Hel' and 'o W'.
+ Matches the preceding pattern element one or more times. 
$string1 = "Hello World\n";
if ($string1 =~ m/l+/) {
  print "There are one or more consecutive letter \"l\"'s in $string1.\n";
}

Output: 

There are one or more consecutive letter "l"'s in Hello World.
? Matches the preceding pattern element zero or one time. 
$string1 = "Hello World\n";
if ($string1 =~ m/H.?e/) {
  print "There is an 'H' and a 'e' separated by ";
  print "0-1 characters (e.g., He Hue Hee).\n";
}

Output: 

There is an 'H' and a 'e' separated by 0-1 characters (e.g., He Hue Hee).
? Modifies the *, +, ? or {M,N}'d regex that comes before to match as few times as possible. 
$string1 = "Hello World\n";
if ($string1 =~ m/(l.+?o)/) {
  print "The non-greedy match with 'l' followed by one or ";
  print "more characters is 'llo' rather than 'llo Wo'.\n";
}

Output: 

The non-greedy match with 'l' followed by one or more characters is 'llo' rather than 'llo Wo'.
* Matches the preceding pattern element zero or more times. 
$string1 = "Hello World\n";
if ($string1 =~ m/el*o/) {
  print "There is an 'e' followed by zero to many ";
  print "'l' followed by 'o' (e.g., eo, elo, ello, elllo).\n";
}

Output: 

There is an 'e' followed by zero to many 'l' followed by 'o' (e.g., eo, elo, ello, elllo).
{M,N} Denotes the minimum M and the maximum N match count.

N can be omitted and M can be 0: {M} matches "exactly" M times; {M,} matches "at least" M times; {0,N} matches "at most" N times.

x* y+ z? is thus equivalent to x{0,} y{1,} z{0,1}. 

$string1 = "Hello World\n";
if ($string1 =~ m/l{1,2}/) {
  print "There exists a substring with at least 1 ";
  print "and at most 2 l's in $string1\n";
}

Output: 

There exists a substring with at least 1 and at most 2 l's in Hello World
[…] Denotes a set of possible character matches. 
$string1 = "Hello World\n";
if ($string1 =~ m/[aeiou]+/) {
  print "$string1 contains one or more vowels.\n";
}

Output: 

Hello World
 contains one or more vowels.
| Separates alternate possibilities. 
$string1 = "Hello World\n";
if ($string1 =~ m/(Hello|Hi|Pogo)/) {
  print "$string1 contains at least one of Hello, Hi, or Pogo.";
}

Output: 

Hello World
 contains at least one of Hello, Hi, or Pogo.
\b Matches a zero-width boundary between a word-class character (see next) and either a non-word class character or an edge; same as

(^\w|\w$|\W\w|\w\W). 

$string1 = "Hello World\n";
if ($string1 =~ m/llo\b/) {
  print "There is a word that ends with 'llo'.\n";
}

Output: 

There is a word that ends with 'llo'.
\w Matches an alphanumeric character, including "_";

same as [A-Za-z0-9_] in ASCII, and

[\p{Alphabetic}\p{GC=Mark}\p{GC=Decimal_Number}\p{GC=Connector_Punctuation}]

in Unicode, where the Alphabetic property contains more than Latin letters, and the Decimal_Number property contains more than Arab digits. 

$string1 = "Hello World\n";
if ($string1 =~ m/\w/) {
  print "There is at least one alphanumeric ";
  print "character in $string1 (A-Z, a-z, 0-9, _).\n";
}

Output: 

There is at least one alphanumeric character in Hello World
 (A-Z, a-z, 0-9, _).
\W Matches a non-alphanumeric character, excluding "_";

same as [^A-Za-z0-9_] in ASCII, and

[^\p{Alphabetic}\p{GC=Mark}\p{GC=Decimal_Number}\p{GC=Connector_Punctuation}]

in Unicode. 

$string1 = "Hello World\n";
if ($string1 =~ m/\W/) {
  print "The space between Hello and ";
  print "World is not alphanumeric.\n";
}

Output: 

The space between Hello and World is not alphanumeric.
\s Matches a whitespace character,

which in ASCII are tab, line feed, form feed, carriage return, and space;

in Unicode, also matches no-break spaces, next line, and the variable-width spaces (amongst others). 

$string1 = "Hello World\n";
if ($string1 =~ m/\s.*\s/) {
  print "In $string1 there are TWO whitespace characters, which may";
  print " be separated by other characters.\n";
}

Output: 

In Hello World
 there are TWO whitespace characters, which may be separated by other characters.
\S Matches anything but a whitespace. 
$string1 = "Hello World\n";
if ($string1 =~ m/\S.*\S/) {
  print "In $string1 there are TWO non-whitespace characters, which";
  print " may be separated by other characters.\n";
}

Output: 

In Hello World
 there are TWO non-whitespace characters, which may be separated by other characters.
\d Matches a digit;

same as [0-9] in ASCII;

in Unicode, same as the \p{Digit} or \p{GC=Decimal_Number} property, which itself the same as the \p{Numeric_Type=Decimal} property. 

$string1 = "99 bottles of beer on the wall.";
if ($string1 =~ m/(\d+)/) {
  print "$1 is the first number in '$string1'\n";
}

Output: 

99 is the first number in '99 bottles of beer on the wall.'
\D Matches a non-digit;

same as [^0-9] in ASCII or \P{Digit} in Unicode. 

$string1 = "Hello World\n";
if ($string1 =~ m/\D/) {
  print "There is at least one character in $string1";
  print " that is not a digit.\n";
}

Output: 

There is at least one character in Hello World
 that is not a digit.
^ Matches the beginning of a line or string. 
$string1 = "Hello World\n";
if ($string1 =~ m/^He/) {
  print "$string1 starts with the characters 'He'.\n";
}

Output: 

Hello World
 starts with the characters 'He'.
$ Matches the end of a line or string. 
$string1 = "Hello World\n";
if ($string1 =~ m/rld$/) {
  print "$string1 is a line or string ";
  print "that ends with 'rld'.\n";
}

Output: 

Hello World
 is a line or string that ends with 'rld'.
\A Matches the beginning of a string (but not an internal line). 
$string1 = "Hello\nWorld\n";
if ($string1 =~ m/\AH/) {
  print "$string1 is a string ";
  print "that starts with 'H'.\n";
}

Output: 

Hello
World
 is a string that starts with 'H'.
\z Matches the end of a string (but not an internal line). 
$string1 = "Hello\nWorld\n";
if ($string1 =~ m/d\n\z/) {
  print "$string1 is a string ";
  print "that ends with 'd\\n'.\n";
}

Output: 

Hello
World
 is a string that ends with 'd\n'.
[^…] Matches every character except the ones inside brackets. 
$string1 = "Hello World\n";
if ($string1 =~ m/[^abc]/) {
 print "$string1 contains a character other than ";
 print "a, b, and c.\n";
}

Output: 

Hello World
 contains a character other than a, b, and c.

외부링크[편집 | 원본 편집]

https://regexr.com/

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